A number of different building appliances may be located within a building or structure. For a typical domestic dwelling, such building appliances may include, a heating, ventilation, and/or air conditioning (HVAC) system, a humidifier/dehumidifier, an air cleaner, a water heater, a pool heater, a water softener, a dishwasher, a security system, a garage door opener, a sprinkler system, an oven, a clothes washer and/or any other suitable building appliance. Often because of cost constraints, some building appliances incorporate a low-cost user interface which has limited capabilities. For example, a low-cost user interface may include a blinking LED light. In some cases, the LED may emit a coded signal indicative of a diagnostic status of the building appliance. To help with maintenance and/or repair of the building appliance, the coded signal may be read and manually decoded by a user in order to derive the diagnostic status of the building appliance.